1. Field of the Invention
The present invention relates to component replacement support tools used for the replacement of a heating roller, a pressure roller, or a lamp cartridge in a fusing unit of an image forming apparatus, such as a laser printer.
2. Description of the Related Art
In an image forming apparatus such as a laser printer or a copy machine, a recording medium with an un-fused toner image carried thereon is heated and pressed between a heating roller and a pressure roller of a fusing unit in order to fuse the toner image onto the surface of the recording medium. The heating roller typically contains heater lamps as a heat source. Generally, as the printing speed or the ream weight increases, the image forming apparatus requires a larger amount of heat for fusing the toner image. Thus, the heating roller needs to be maintained at higher temperatures in order to provide higher fusing temperatures.
When the heating roller is replaced at the end of its lifespan, typically a maintenance worker first needs to stop the operation of the image forming apparatus and then wait until the heating roller is cooled down to a temperature allowing the removal of the heating roller from the fusing unit for replacement. In this case, however, it takes a long time before the heating roller is sufficiently cooled, resulting in low operation efficiency. The image forming apparatus also needs to be stopped for a long time during the replacement work, resulting in not only a decrease in the operational efficiency of the image forming apparatus but also in an increase in the replacement/maintenance cost.
In recent years, there has been an increasing need for higher printing speed and image quality, and also for the capability for handling various kinds of printing sheets. When high-speed printing is required, the surface of the heating roller may be coated with a thin layer of a PFA (tetrafluoroethylene/perfluoroalkylvinylether copolymer) resin so that the heat for fusing the toner image can be quickly transmitted from the heating roller to the recording medium. When a higher image quality is required, the surface of the heating roller may be coated with silicon rubber so that the toner image can be prevented from being blurred or stained on the recording medium upon fusing. When the durability of the heating roller is of concern while a certain level of image quality also needs to be maintained, the silicon rubber layer of the heating roller may be coated with PFA tube. Thus, there is a demand for the use of several kinds of heating rollers.
Such demand may be addressed by providing various heating rollers in a single image forming apparatus so that one of the heating rollers can be selected depending on the requirement. However, the heating rollers generally have large thermal capacities, although there may be some differences depending on the type of the heating roller. Thus, a long time is generally required before any of the heating rollers is cooled down from the high temperature for fusing to a lower temperature for replacement.
FIG. 1 is a cross section of a portion of a fusing unit discussed in JP05-504633A. FIG. 2 is a perspective view illustrating how the fusing unit is replaced. As illustrated in FIG. 1, one end of the heating roller 100 is supported on a frame 102 via a support flange 101. The support flange 101 is fitted in an open end of the heating roller 100 together with a centering member 104 via a bearing 103. While not illustrated, the other end of the heating roller 100 is similarly supported on another support flange via a bearing. The support flange 101 is fixed to the frame 102 by a thumbscrew 106. A retaining nail 108 is attached to the support flange 101 via a thumbscrew 107. The retaining nail 108 is configured to fix the heating roller 100 at the time of replacing the heating roller 100.
In the heating roller 100, plural heater lamps 105 are disposed of which one end is retained at the center of the support flange 101 via a retaining member 109. While not illustrated, the other end of the heater lamps 105 is similarly retained on the corresponding support flange via a retaining member. A connector 110 is disposed at the end of the heater lamps 105. With the heater lamps 105 retained at the center of the support flange 101, the connector 110 protrudes beyond the support flange 101, as illustrated in FIG. 1. To the support flange 101, a grip 111 is integrally attached which is used when replacing the heating roller 100. The grip 111 is disposed to straddle over the connector 110.
When replacing the heating roller 100, the thumbscrew 106 is unfastened and the heating roller 100 is pulled out of the frame 102, together with the support flange 101 or the like, while holding the grip 111 with one hand, as illustrated in FIG. 2. The opening of the frame 102 may be lined with felt so as to prevent damage to the heating roller 100 upon contacting the frame 102.
The heating roller 100 is typically a cylinder having a diameter of about 100 mm and a length of about 500 mm or more, with more than a little weight. Accordingly, in the case of the fusing unit according to Patent Document 1, it is not easy for the maintenance worker to pull the heating roller 100 out of the frame 102 together with the support flange 101 and the like stably. Specifically, even though the grip 111 is held with one hand and the heating roller 100 is held with the other gloved hand 120, the pulling-off operation may be destabilized due to the weight of the heating roller 100 and heat. As a result, the heating roller 100 may come into contact with other components, such as the frame 102, resulting in a damage to the roller surface.
Thus, according to the above conventional technology, the posture of the heating roller 100 tends to be unstable and no supporting tool is described for stabilizing the posture of the heating roller 100. There is also the danger of burning the hands of the maintenance worker by the high-temperature heating roller 100 even if the hands are gloved. Further, a mold release agent or lubricant on the heating roller 100 may become attached to the gloved hand 120, thereby not just staining the hand but also hindering the replacing operation.
Further, when the heating roller 100 is pulled out of the frame 102 together with the support flange 101 and the like by holding the grip 111 with one hand, the roller surface may be scratched upon contact with the frame 102. While the opening of the frame 102 may be lined with felt for protection of the heating roller surface, the mold release agent or lubricant on the heating roller 100 may be transferred onto the felt and may remain on the felt as dirt, which may potentially damage the surface of the heating roller 100. The felt also needs to be affixed and removed each time the heating roller 100 is replaced. The removed felt needs to be disposed of and new felt needs to be prepared.
In order to prevent the damage to the heater lamps when pulling them out, JP2002-23535A proposes the following. FIG. 3 is a cross section of a lamp cartridge 127 discussed in this publication. When pulling the lamp cartridge 127 out of a heating roller 114, an operator moves to the rear of the image forming apparatus (the side of a second lamp holder 129; i.e., to the left of FIG. 3). The operator then inserts a lamp protection member 164 into a through-hole 159a of a housing 159 until an inner circumferential portion of the lamp protection member 164 is fitted in a retaining portion 130 of the first lamp holder 128, thus securely positioning the lamp protection member 164.
The operator then moves to the front of the image forming apparatus (i.e., to the right-side of FIG. 3 where the first lamp holder 128 is disposed) and withdraws a regulating member 165 from a concave portion (not shown) formed in the first lamp holder 128, thus freeing the regulation of the movement of the lamp cartridge 127 in an axial direction. Then, the lamp cartridge 127 is pulled out of the heating roller 114 together with the lamp protection member 164.
In this method, damage to the lamp cartridge 127 upon its detachment or attachment may be prevented and the lamp cartridge 127 may be handled more easily. However, the lamp protection member 164 cannot be used for replacing the heating roller 114; namely, a separate jig is required for replacing the heating roller 114, thus requiring various jigs. In addition, the jigs for replacing the lamp protection member 164 and the heating roller 114 need to be individually managed and stored, requiring additional space for the replacing operation or during storage.
When the lamp protection member 164 is inserted into the image forming apparatus until the front end of the lamp protection member is fitted in the first lamp holder 128, how far the lamp protection member 164 should be inserted has been left to the discretion of the individual operator based on experience or guess-work. Consequently, the operator may decide to pull the lamp cartridge 127 when the lamp protection member 164 is not fully fitted in the first lamp holder 128, thereby potentially damaging the lamp cartridge 127.
When a new lamp cartridge 127 is attached within the image forming apparatus, the lamp protection member 164 (lamp cartridge 127) is inserted from the right of FIG. 3 such that the lamp protection member 164 can pass through central openings of heating roller lids 115a and 115b of the heating roller 114. In this case, because the inside of the image forming apparatus cannot be visually monitored with the naked eye, it is difficult to pass the lamp protection member 164 through the central openings, particularly the one in the heating roller lid 115b located down the inserted direction.